Clutch for sound recorders



p 14, 1965 J. a. WALLACE ETAL 3,206,212

CLUTCH FOR SOUND RECORDERS 2 Sheets-Sheet 1 Filed May 11 1962 INVENTORS. Will/9C5 MERLE b- 62/5 W040 P 1955 J. G. WALLACE ETAL 3,206,212

CLUTCH FOR SOUND REGORDERS Filed May 11, 1962 2 Sheets-Sheet 2 INVENTORS. JO/X/V 6'- W/VLLICE United States Patent 3,206,212 CLUTCH FOR SOUND RECORDERS John G. Wallace, Branford, and Merle H. Griswold, Trumbull, Conn., assignors to Dictaphone Corporation, Bridgeport, Conn a corporation of New York Filed May '11, 1962, Ser. No. 193,964 14 Claims. (Cl. 27417) The present invention relates to a clutch for controlling transmission of power and more particularly to a clutch requiring an extremely small force to engage and disengage to adapt it for starting and stopping a record in a sound recording and reproducing machine.

One type of sound recording and reproducing machine, commonly known as a dictating machine, is used extensively in offices and the like for recording and reproducing dictation. Most machines of this type are operated by current from power service lines. In recent years, however, portable sound recording and reproducing machines have been developed which are adapted to be carried from place to place. Portable machines are operated by electric batteries so that it is particularly desirable to reduce the power required and, in turn, to reduce the size and weight of the machine as well as the size and weight of the batteries used to operate the machine. Moreover, it would be particularly desirable to provide an improved control clutch of a design to meet the requirements of portable machines which also could be used interchangeable in machines operated from power service lines.

One of the objects of the present invention is to provide an improved electro-magnetically operated control clutch which is operated by an extremely small current and maintained in operation by a small fraction of the operating current.

Another object is to provide an improved clutch of the type indicated which is engaged by merely rocking a freely movable armature in one direction and disengaged by the movement by the clutch itself to reduce to a minimum the forces required to control the machine.

Still another object is to provide a clutch of the type indicated which is of simple and compact construction, economical to manufacture and one which is reliable in operation.

These and other objects will become more apparent from the following description and drawings in which like reference characters denote like parts throughout the several views. It is to be expressly understood, however,

that the drawings are for the purpose of illustration only and are not a definition of the limits of the invention, reference being had for this purpose to the appended claims.

In the drawings:

FIGURE 1 is a diagrammatic view in perspective showing a driving mechanism for the record belt of a sound recording and reproducing mechanism and incorporating the clutch of the present invention;

FIGURE 2 is an enlarged transverse sectional view taken on line 2-2 of FIGURE 1 to show the magnetic armature operated to a clutch driving position;

FIGURE 3 is a side elevational view of a part of the clutch to show the relationship of the detents and clutch pawl on the driving and driven elements when the armature is withdrawn;

FIGURE 4 is a view similar to FIGURE 2 showing the magnetic armature released to trip the pawl and disengage the clutch;

FIGURE 5 is a side elevational view showing the relationship of the trip with respect to the pawl before the clutch is disengaged;

3,206,212 Patented Sept. 14, 1965 FIGURE 6 is a side elevational view of a part of the clutch similar to FIGURE 5 and showing the manner in which the pawl is disengaged as it moves with respect to the trip pin on the armature; and

FIGURE 7 is a sectional View taken on line 77 of FIGURE 4 to show the pawl releasing mechanism in full when locked in its disengaged position.

Referring now to the drawings, the clutch 10 of the present invention is shown applied to a drive for operating the record 11 of a sound recording and reproducing machine. In FIGURE 1 of the drawings, the frame and other parts of the machine have not been shown so as to more clearly illustrate the clutch 10 and drive for the record 11.

The record 11 is illustrated in the form of a continuous web or belt mounted on and stretched over a pair of mandrels 12 and 13. Mandrel 12 is driven while mandrel 13 is an idler and the two mandrels are mounted for relative movement toward each other to adapt record belts to be placed on and removed from the mandrels. While not shown, it will be understood that the record belt moves relative to a stylus which produces a groove in the record belt having undulations corresponding to variations in the sound being recorded.

Mandrel 12 is driven from a motor 14 through a speed reduction drive 15 including the clutch 10 of the present invention. The drive comprises a small pulley 16 on the shaft of motor 14 and connected to a larger pulley 17 of the clutch 10 by a belt 18 to provide one speed reduction. A smaller pulley 19 of clutch 10 is selectively driven from the large pulley 17 through a clutch pawl 20 which, in turn, drives a larger pulley 21 on a shaft 22 for the mandrel 12 through a belt 23 to provide a second speed reduction. Operation of the motor 14 is controlled by a switch 24 for connecting the motor to a source of power, such as an electric battery 25, when the machine is to be operated. The motor 14 then runs continuously and operation of the record belt 11 is controlled by clutch 11) which, in turn, is controlled by an electric circuit 26 from the battery including a control switch 27.

In accordance with the present invention, the clutch 10 comprises the driving and driven pulleys 17 and 19 adapted to be connected and disconnected by pawl 20 and an operating mechanism for controlling the pawl. In the illustrated embodiment the clutch comprises a generally T shaped mounting plate 29, see FIGURE 1, which, in turn, mounts the clutch on a plate 30 or" the machine frame, see FIGURE 2. The pulleys 17 and 19 of the clutch 10 are mounted one on the other to rotate relative to each other on a fixed shaft 31 projecting from one side of the mounting plate 29. An electromagnet 32, later to be described in detail, is mounted in an opening in the mounting plate 29 and projects from the side thereof opposite the pulleys 17 and 19. An armature 33 extends radially at opposite sides of the shaft 31 and mounts a pin 34 at one end for movement laterally to engage the clutch pawl 20 and a pin 35 at its opposite end extends through the mounting plate 29. A spring 36 acting between the mounting plate 29 and a collar 37 on pin 35 tends to rock the armature 33 on a pivot 38, struck inwardly from mounting plate 29, to stopping position, while the electro-magnet 32 operates to rock the armature against the action of the spring to a starting and running position. The mounting plate 29 and armature 33 are shown positioned so that the armature extends vertically for convenience of illustration, but it will be understood that the plate 29 and armature 33 can be rotated 90 from the position shown so that the armature extends horizontally.

The electro-magnet 32 comprises a cylindrical casing 40 having a cylindrical core 41 of less diameter than the cylindrical casing and arranged axially therein. A circular plate 42 at one end of core 41 closely fits the outer end of the cylindrical housing to form an annular channel 43 between the casing and core for mounting the electromagnetic winding 44 therebetween. The outer periphery of the circular plate 42 is attached to the cylindrical casing as by welding, or the like, to form a one-piece structure having a low magnetic reluctance. The inner ends of the cylindrical outer casing 49 and core 41 are machined normal to the common axis so that the core provides one pole while the radially spaced peripheral end of the casing provides the other pole of an electro-magnet. The core 41 of the electro-magnet 32 has an axial bore 45 through which a reduced end 31a of the shaft 31 extends to provide an annular shoulder 31b engaging the end of the core. The outer end of the reduced shaft portion 31a is threaded at 310 on which a nut 46 is screwed against the opposite end of the core to attach the shaft thereto. The outer cylindrical housing 40 is fixedly attached to the mounting plate 29 as by welding or brazing, the core 41 is fixedly attached to the outer end of the cylindrical housing and the shaft 31 is fixedly attached to the core and projects laterally from the left-hand end thereof as viewed in FIGURE 2.

In general, the larger pulley 17 is mounted to rotate on the smaller pulley 19 and the pawl 20 connects the two pulleys for rotation as a unit. To this end, a radial disc 51 is fixedly attached to the inner or right-hand end of smaller pulley 19 as by welding or brazing and the outer periphery of the disc 51 is offset laterally and formed with a peripheral slot 52. Pawl 20 is positioned in said slot 52 and mounted to rock on a pin 53 extending across said slot. Referring to FIGURES 3, 5, 6 and 7, a spring 54 acting between the disc 51 and one end of the pawl tends to rock the pawl radially.

The large pulley 17 has a bushing 55 pressed into it which serves as its bearing surface as it rotates about the small pulley 19. The large pulley also has an inner hub 56 contacting the disc 51 and an inwardly extending outer rim 57 which, with the inner hub, form an annular recess therebetween and into which the laterally offset portion of the disc projects. Larger pulley 17 is held in position on the small pulley 19 by means of a retaining snap ring 58 extending into a groove 59 in the small pulley 19 and a recess 60 in the pulley. Thus, the pawl 20 pivotally mounted in the slot 52 in disc 51 underlies the peripheral rim 57 of the larger pulley. Pulley 19, in turn, is mounted to rotate on bushings 61 and 62 on shaft 31 and is held in place by a collar 63 and snap ring 64 on the shaft.

Mounted on and forming a part of the inner periphery of the outer rim 57 of the pulley 17 is a ring 65 having a series of radially spaced detents 66 projecting inward for engagement by the end of the pawl 20. The ring 65 may be formed of any suitable material, but one which has been found satisfactory in an acetal plastic, Celcon, manufactured by Celanese Polymer Corporation and molded in place on the rim.

The pawl 20 is of generally arcuate shape, as shown most clearly in FIGURES 5 to 7, and having a shoulder 70 at one end for engaging a shoulder 71 on one of the detents 66 to lock the disc 51 and inner pulley 19 to the outer pulley 17 for rotation as a unit. Rearwardly of the shoulder 70, the pawl 20 has a notch 72 in its outer edge for locking engagement with the pin 34 projecting from armature 33, see FIGURES 2 and 4, and rearwardly of the notch 72 is a curved cam face 73 which inclines radially from the outer periphery of the disc 51 to the inner periphery of rim 57 of pulley 17 when the pawl is in driving engagement with pulley. The opposite edge of the pawl 20 has a recess 74 for receiving one end of the spring 54 acting between it and the disc 52 to engage pawl 20 with pulley 17.

Armature 33 is in the form of a plate composed of a magnetic material and having a central opening 75 through which the shaft 31 extends so that the armature extends radially at opposite sides of the shaft. Pivot 38 on mounting plate 29 is constructed of a non-magnetic material, such as brass, to prevent shorting of the magnetic path and the pivot is formed with an edge 77 on which the armature is adapted to rock from the position illustrated in FIGURE 2 to that illustrated in FIGURE 4. As will be observed by reference to FIGURE 2, the armature 33 is moved into spaced parallel relationship with the disc 51 (when the electro-magnetic winding 44 is energized) to remove trip pin 34 from the path of pawl 20 and is rocked about the edge 77 by the spring 36 (when the electro-magnetic winding is de-energized) to position the pin 34 in the path of movement of the pawl 20.

The parts including the electro-magn-et 32 and armature 33 are so designed as to require a minimum current to operate the armature and only a fraction of the operat ing current to hold the armature. For example, a clutch made in accordance with the present invention for controlling a sound recording and reproducing machine required only milliamperes to operate, and once the armature was engaged, a delayed action device illustrated diagrammatically at 80 in FIGURE 1 reduced the current to only 5 milli-amperes which held the armature. A small gap 78 also is provided in the magnetic flux path so that the armature 33 will not be held by residual magnetism after coil 44 is de-energized. In the illustrated embodiment this gap 78 is formed as an electroplated layer of a non-magnetic metal such as chromium, on the contacting surfaces of the armature 33 and magnet casing 40 and core 41. A push pin 79 also is provided on armature 33 which projects laterally therefrom, see FIGURE 2, for mechanically operating the armature 33 (by mechanism not shown) to clutch releasing position while the magnet 32 is energized. When once released the armature will remain released because of the small magnetic holding force. One form of the invention having now been described in detail, the mode of operation is next explained.

When it is desired to operate the sound recording and reproducing machine the switch 24 is closed to energize the motor 14 which, operating through the pulley 16 and belt 15, rotates the pulley 17 of the clutch 10. When the record belt 11 is to be operated the switch 27 is closed to energize the electro-magnet 32 of the clutch 10. Upon energization of the electro-magnet, a magnetic flux path is set up between the core 41 constituting one pole, the outer casing 40 constituting the other pole and through the armature 33. The magnetic field then produces a magnetic force on the armature 33 to draw it to the position illustrated inFIGURE 2 where it engages the left-hand end of the casing to produce a path of lowest magnetic reluctance. Such movement of the armature 33 withdraws the pin 34 from the path of movement of the pawl 20. Pawl 20 then is operated by the spring 54 to engage the shoulder 70 at its end with the shoulder 71 of a detent 65 on the inner periphery of the large pulley 17 as illustrated in FIGURE 5. As the outer pulley 17 is driven by the belt 18, its motion is transmitted through the pawl 20 to the disc 52 and small pulley 19 extending outwardly therefrom to drive the inner and outer pulleys as a unit. The inner pulley 19 then operates through the belt 23 to operate the larger pulley 21 on the mandrel shaft 22 to rotate the mandrel 12. Record belt 11 is then driven relative to a stylus for recording sound thereon.

This operation continues until the record belt is to be stopped. This is accomplished by opening the switch 27 in the circuit 26 for the electromagnetic winding 44 which is then de-energized- Upon de-energization of the winding 44, the spring 36, see FIGURE 4, acting between the mounting plate 29 and collar 37 on pin 35, rocks the armature 33 about the pivot 38 from the position illustrated in FIGURE 2 to that illustrated in FIGURE 4. Such rocking movement of the armature 33 positions the pin 34 in the path of movement of the pawl 20 as illustrated in FIGURES 4 and 5. As the pawl 29 moves relative to the pin 34 the curved cam surface 73 at the outer edge of the pawl engages the trip pin 34 which rocks the pawl on the pivot pin 53 against the action of the spring 54 to release its driving shoulder 70 from engagement with the shoulder 71 of the detent 65. Disengagement of shoulder 70 on the pawl 20 from shoulder 71 on pulley 17 interrupts the driving connection between the driving and driven pulleys .17 and 19. The pawl 20 and disc 51 on which it is mounted then continue to move from the position illustrated in FIGURE 6 to that illustrated in FIGURE 7 until the pin 34 enters the groove 72 in the edge of the pawl to lock it in released position. Pawl then remains in released position under the influence of the spring 36 until the winding 44 of the electro-magnet 32 is again energized to rock the armature 33 to releasing position, as illustrated in FIGURE 2.

It will be noted that the clutch 10 is controlled by the pin 34 which is moved laterally by the armature 33 in a direction at right angles to the plane of movement of the pawl 20. The only force required to start or stop operation of the sound recording and reproducing apparatus is that required to rock the relatively light armature 33, either magnetically, as illustrated in FIGURE 3, or by means of the spring 36, as illustrated in FIGURE 4. The actual work of disconnecting the driving and driven members 17 land 19 is produced by the longitudinal pull on the armature 33 against the shaft 31 as the pin 34 and pawl 20 move relative to each other. As a result of the above described construction, the electromagnetic winding 44 in a particular installation requires only a small'current of 80 milli-amperes to operate the armature 33 from the position illustrated in FIGURE 4 to that illustrated in FIGURE 2. After the armature has been operated a small current of only 5 millieamperes is sufirc-ient to hold the armature retracted due to the efiiciency of the magnetic circuit.

It will now be observed that the present invention provides an improved electro-magnetically operated control clutch requiring a minimum current to operate to a starting position and an even lesser current to maintain the clutch in operation. It will further be observed that the present invention provides a construction in which the movement of the parts of the clutch are utilized to disengage the clutch to reduce the force required to a minimum. It will still further be observed that the present invention provides a clutch which is of simple and compact construction, economical to manufacture and one which is reliable in operation.

While a single embodiment of the invention is herein illustrated and described, it will be understood that further changes may be made in the construction and arrangement of the elements without departing from the spirit .or scope of the invention. Therefore, without limitation in this respect, the invention is defined by the following claims.

What is claimed is:

-1. In a sound recording and reproducing machine of the type having a movable record, a prime mover and a rotating element driven from the prime mover for moving the record, the combination with the elements of such a machine of a stationary frame, a clutch for controlling operation of the rotating element comprising a driving element connected to the prime mover, a driven element connected to the rotating element, a pawl mounted on one of the elements for movement into and out of engagement with the other element and having an arcuate edge therebetween, a control member mounted on the stationary frame for movement parallel to the axis of rotation of the driven element at a location between the pawl and element its engages for engaging and disengaging the armate edge of the pawl, a spring to yieldingly move the control member into engagement with the pawl, and an electromagnet for actuating the member to a second disengaging position against the saction of the spring.

2. In a sound recording and reproducing machine having a pulley for driving a record, a motor, a transmission between the motor and pulley including a clutch having a driving member connected to the motor, a driven member connected to the pulley, a pawl mounted on and rotatable with one of the members and having a cam surface on one side, a detent on the other member engaged by said pawl, resilient means for yieldingly engaging the pawl with the detent, a stationary frame, a control element having a pin projecting from one side and pivotally mounted on the frame for rocking movement laterally into and out of the path of movement of the pawl, a spring for rocking the control element in one direction to engage the pin on the control element with the cam surface on the pawl whereby the rotary movement of the pawl relative to the pin provides the force required to disconnect the clutch, and an electro-magnet for actuating the control element in the opposite direction against the action of the spring.

3. A sound recording and reproducing machine in accordance with claim 2 in which the machine has a mandrel for mounting a belt type record, the pulley is attached to the mandrel, and the clutch comprises a selfcontained unit including a bracket for mounting it on the machine.

4. A sound recording and reproducing machine in accordance with claim 2 in which the driving member is a pulley, the driven member is a pulley projecting laterally from the first pulley, and belts connecting the motor to the driving pulley and the driven pulley to the pulley for driving the recor 5. A sound recording and reproducing machine in accordance with claim 4 in which the driving and driven pulleys are arranged concentrically, and the detent and pawl being mounted on the driving and driven pulleys, respectively, between concentric parts thereof.

6. In a sound recording and reproducing machine for driving a belt type record, a pulley connected to drive the record belt, a motor, a transmission between the motor and pulley and a combined clutch and speed reducing device comprising a driven pulley, a driving pulley connected to the motor and mounted to rotate on the driven pulley, said driven pulley extending laterally beyond the side of the driving pulley and connected to drive said pulley for the record belt, a pawl pivot-ally mounted on one of the clutch pulleys, a detent on the other clutch pulley, a spring for yieldingly rocking the pawl on said one pulley into engagement with the detent on said other pulley, a control member extending radially at one side of the pulleys and having a pin projecting parallel to the axis of the pulleys, at a location between the pawl and clutch element it engages, a spring for actuating the control member in one direction to position the pin in the path of movement of the pawl, and an electro-magnet for actuating the control member against the action of the action of the spring to withdraw the pin from the path of movement of the pawl.

7. A sound recording and reproducing machine in accordance with claim 6 in which the driven pulley of the combined clutch and speed reducing device has a hub and is mounted to rotate on a shaft, the driving pulley is mounted to rotate on the driven pulley and has a laterally projecting rim overlying the hub on the driven shaft, a pulley on the motor having a diameter less than the diameter of the driving pulley, a belt connecting the motor and driving pulley to produce a speed reduction, the pulley for driving the record belt having a larger diameter than the driven pulley, and a belt connecting the last mentioned pulleys to produce a second speed reduction between the motor and record belt being driven.

8. A sound recording and reproducing machine in accordance with claim 6 in which the driven pulley of the combined clutch and seped reducing device has a hub and is mounted to rotate on a shaft, the driving pulley is mounted to rotate on the driven pulley and has a laterally projecting rim overlying the hub on the driven pulley, the pawl being pivotally mounted on the driven pulley and extending radially and circumferentially'to provide a curved cam surface on its outer periphery for engagement by the pin on the control element, and the laterally projecting n'm having a plurality of circumferentially spaced detents projecting radially inward for engagement by the pawl.

9. In a sound recording and reproducing machine hav ing a pulley for driving a record belt, a driving member,- a driven member, said driving and driven members being arranged in overlying relationship and having radial spaced parts, a clutch pawl pivotally mounted on one member and having an arcuate edge, a detent on the other member for engagement by the pawl, resilient means y-ieldingly actuating the pawl into driving engagement with the detent to provide a driving connection between the members, an electro-magnet having an armature on the electro-magnet for movement parallel to the axis of rotation of the driven member, means for mounting the armature to permit limited lateral rocking movement and restrain it against longitudinal movement, said armature having an abutment projecting therefrom between the pawl and element it engages in one rocked position 'thereofforengagement .by the arcuate edge of the pawl and located at one, side -of the pawl in another rocked position to disengage the arcuate edge of the pawl, a spring for rocking the armature to one position, and said armature being moved by said electromagnet to said other position whereby the electro-magnet requires only the current necessary to produce a force greater than the spring force to rock the armature and initiate operation of the machine and a minimum current to hold the armature retracted.

10. A sound recording and reproducing machine in accordance with claim 9 in which the armature has the abutment pin projecting from one end and an anchoring pin projecting from its opposite end, a mounting plate through which the anchoring pin extends, and the spring acting between the abutment on the anchoring pin and plate.

11. A sound recording and reproducing machine in accordance with claim 10 in which a pivot for the 'armature is provided on the-mounting plate between the anchoring pin and clutch releasing abutment, and said electro-magnet being located adjacent the pivot to position the armature close to the electro-magnet when rocked away from the latter.

12. A sound recording and reproducing machine in accordance with claim 9 in which the magnet comprises a cylindrical casing, a circular plate having an axial core projecting laterally from one side thereof to provide an annular opening between it and the cylindrical casing, an electric coil in said annular opening to provide an electro-magnet, and the armature is a keeper bar extending across the end of the hub and flange to produce a magnetic path of minimum reluctance.

13. A clutch for controlling transmission of power from a driving member to a driven member comprising a pawl mounted on and rotatable with one of said members, at least one detent on the other member, resilient means for yieldingly actuating the pawl into driving engagement with the detent, and meansfor controlling the pawl comprising a cam face onone side thereof, a stationary frame, a magnetic armature having an actuator projecting from one side and mounted on the frame, to rock from a position where the actuator overlies the cam face on the pawl to a second position where the actuator is withdrawn laterally from the plane of the pawl, a spring for producing a force on one side of the armature only slightly greater than that necessary to rock the armature in one direction, and an electro-magnet for rocking the armature against the action of the spring whereby to operate the clutch by the application of the minimum force required to rock a freely movable arm. I

14. A clutch in accordance with claim 13 in which a mechanical actuator projects from one side of the armature for actuating the latter to a clutch disengaging position against the action of the electro-magnet.

References Cited by the Examiner UNITED STATES PATENTS NORTON ANSHER, Primary Examiner. 

1. IN A SOUND RECORDING AND REPRODUCING MACHING OF THE TYPE HAVING A MOVABLE RECORD, A PRIME MOVER AND A ROTATING ELEMENT DRIVEN FROM THE PRIME MOVER FOR MOVING THE RECORD, THE COMBINATION WITH THE ELEMENTS OF SUCH A MACHINE OF A STATIONARY FRAME, A CLUTCH FOR CONTROLLING OPERATION OF THE ROTATING ELEMENT COMPRISING A DRIVING ELEMENT CONNECTED TO THE PRIME MOVER, A DRIVEN ELEMENT CONNECTED TO THE ROTATING ELEMENT, A PAWL MOUNTED ON ONE OF THE ELEMENTS FOR MOVEMENT INTO AND OUT OF ENGAGEMENT WITH THE OTHER ELEMENT AND HAVING AN ARCUATE EDGE THEREBETWEEN, A CONTROL MEMBER MOUNTED ON THE STATIONARY FRAME FOR MOVEMENT PARALLEL TO THE AXIS OF ROTATION OF THE DRIVEN ELEMENT AT A LOCATION BETWEEN THE PAWL AND ELEMENT ITS ENGAGES FOR ENGAGING AND DISENGAGING THE ARCUATE EDGE OF THE PAWL, A SPRING TO YIELDAGLY MOVE THE CONTROL MEMBER INTO ENGAGEMENT WITH THE PAWL, AND AN ELECTRO-MAGNET FOR ACTUATING THE MEMBER TO A SECOND DISENGAGING POSITION AGAINST THE ACTION OF THE SPRING. 